Duke Treadmill Score Calculator
Enter your treadmill exercise duration (Bruce protocol), the maximum ST-segment deviation recorded during or after the test, and your angina response. The calculator returns your Duke Treadmill Score and places it in the validated low-, intermediate-, or high-risk band, along with estimated 5-year survival and annual mortality. Results update as you type.
Formula
Worked example
A patient completes 9 minutes on the Bruce protocol with 1 mm of ST depression and non-limiting angina (index = 1): DTS = 9 - (5 x 1) - (4 x 1) = 9 - 5 - 4 = 0, which falls in the intermediate-risk band (5-year survival ~90%).
What is the Duke Treadmill Score?
The Duke Treadmill Score (DTS) is a validated composite index developed at Duke University Medical Center and published in the New England Journal of Medicine in 1991. It combines three pieces of information obtained from a standard treadmill exercise test: the total duration of exercise, the maximum ST-segment deviation recorded on the electrocardiogram, and whether angina developed during the test. The result is a single number that stratifies patients with suspected coronary artery disease into low-, intermediate-, and high-risk groups for cardiovascular events. Scores typically range from -25 (highest risk) to +15 (lowest risk). The score is used as a decision-support tool to determine whether a patient needs further investigation such as coronary angiography or can be safely managed with medical therapy alone.
How the Duke Treadmill Score formula works
The formula is: DTS = exercise duration (minutes) - (5 x maximum ST deviation in mm) - (4 x angina index). Exercise duration is measured in total minutes on the treadmill following the standard Bruce protocol, where each three-minute stage increases both speed and incline. Longer exercise time raises the score (better prognosis). Maximum ST deviation is the largest net ST change - either depression or elevation - seen in any lead except aVR; each millimetre subtracts 5 points because ST changes signal ischaemia. The angina index scores 0 for no angina, 1 for angina that did not stop the test, and 2 for angina that forced the test to stop; each unit subtracts 4 points because exercise-limiting chest pain implies more severe ischaemia. A score of 5 or above indicates low risk, -10 to 4 is intermediate risk, and -11 or below is high risk.
Understanding the Bruce protocol and exercise duration
The Bruce protocol is the most widely used treadmill stress test protocol in clinical practice. It starts at 1.7 mph with a 10% grade (Stage 1, approximately 4.6 METs) and increases speed and gradient every three minutes. Stage 2 (2.5 mph, 12%) reaches about 7 METs; Stage 3 (3.4 mph, 14%) about 10 METs; Stage 4 (4.2 mph, 16%) about 13 METs. Reaching Stage 3 or 9 minutes represents average fitness for most adults. The Modified Bruce protocol adds two gentler warm-up stages (0% and 5% grade at 1.7 mph) before beginning the standard sequence, and is used for elderly or deconditioned patients. Exercise duration is the single most powerful component of the Duke score: every additional minute on the treadmill adds 1 point, and patients who cannot complete even Stage 1 often fall into the high-risk group regardless of their ECG changes.
Clinical use and limitations
The Duke Treadmill Score is best suited to patients without baseline ECG abnormalities that would make ST interpretation unreliable, such as left bundle branch block, ventricular pre-excitation (Wolff-Parkinson-White syndrome), paced rhythms, or significant resting ST changes. It performs less well in women, in whom exercise-induced ST depression is less specific for ischaemia, and its original validation was based primarily on a population referred for coronary angiography, which may overestimate risk in lower-prevalence community populations. The score should not be used as the sole basis for clinical decisions; it is one input alongside symptoms, risk factor burden, resting ECG findings, imaging results, and the overall clinical picture. High-risk scores (below -11) are associated with approximately 74% prevalence of three-vessel or left main coronary artery disease and generally warrant prompt referral for coronary angiography.
Duke Treadmill Score risk bands
| Score | Risk group | 5-year survival | Annual mortality |
|---|---|---|---|
| >= 5 | Low | 97% | 0.25% |
| -10 to 4 | Intermediate | 90% | 1.25% |
| <= -11 | High | 65% | 5.25% |
Risk stratification categories from the original Duke University validation study (Mark et al., NEJM 1991).
Frequently asked questions
What is a good Duke Treadmill Score?
A score of 5 or above is classified as low risk and is associated with a 5-year survival rate of approximately 97% and an annual cardiovascular mortality of about 0.25%. Such patients can usually be managed with medical therapy and lifestyle modification without urgent further investigation.
What does a negative Duke Treadmill Score mean?
A negative score simply means that the ST deviation and angina terms together outweigh the exercise duration term. A score between -10 and 0 falls in the intermediate-risk band. A score of -11 or below is considered high risk, carrying an estimated 5-year survival of 65% and annual mortality around 5.25% in the original validation cohort.
How is the angina index scored?
The angina index has three values: 0 if no chest pain occurred during the test, 1 if typical angina developed but you were able to continue exercising, and 2 if angina was severe enough that it was the primary reason the test was stopped. Each unit of the angina index subtracts 4 points from the total Duke score.
Can the Duke Treadmill Score be used in women?
The score can be applied to women but has somewhat lower diagnostic accuracy. Exercise-induced ST depression is less specific for obstructive coronary artery disease in women, meaning the ST component may overestimate risk. Some evidence supports giving the angina and functional capacity components more weight in women, and stress imaging (echocardiography or nuclear perfusion) is often recommended as an alternative or complement.
Does a low-risk score mean I do not have coronary artery disease?
Not necessarily. The Duke Treadmill Score predicts cardiovascular event risk and survival rather than ruling out any degree of coronary artery disease. Some patients with low-risk scores have mild coronary disease that is haemodynamically unimportant. The score helps guide management decisions, but clinical judgement and the full test result are always needed.
What happens if I cannot complete the Bruce protocol?
Inability to complete even Stage 1 (less than 3 minutes) is itself a strong adverse prognostic marker. The Modified Bruce Protocol, which begins at lower intensities, is an option for elderly or deconditioned patients. The score formula remains the same regardless of which Bruce variant is used, as long as the duration is recorded accurately in minutes.
Is the Duke Treadmill Score valid if I have a left bundle branch block or a pacemaker?
No. The score relies on interpretable ST changes, which are absent or non-specific in patients with left bundle branch block, right bundle branch block with baseline ST changes, ventricular pacing, Wolff-Parkinson-White syndrome, or significant resting ST depression. In these patients, stress imaging (stress echo or nuclear scan) should be used instead.